JAKARTA - Countries around Asia on Tuesday stepped up the search for an AirAsia plane carrying 162 people that is presumed to have crashed in shallow waters off Indonesia, as television showed pictures of objects that could be debris from the jet.

Soelistyo, head of Indonesia's search and rescue agency, told media the search area in the Java Sea between the islands of Sumatra and Borneo would be expanded.

Authorities would also begin scouring smaller islands and coastal land on Indonesian Borneo, while the United States said it was sending a warship to help in the search.

There have been no confirmed signs of wreckage from the Airbus A320-200 operated by Indonesia AirAsia, which disappeared in poor weather early on Sunday during a flight from the Indonesian city of Surabaya to Singapore.

The missing plane, with most of those on board Indonesian, could be at the bottom of the sea, Soelistyo said on Monday.

Indonesia's Kompass TV showed pictures of what looked like large, angular objects floating in the sea. One appeared to be orange and another grey or brown. The largest appeared to be several metres long.

"Hopefully, we will find something definite because I haven't received anything else," air force official Dwi Putranto told MetroTV referring to the reported debris.

The Java Sea is relatively shallow, making it easier to spot wreckage in the water, say oceanographers, but strong currents and winds mean any debris would be drifting up to 50 km (31 miles) a day east, away from the impact zone.

"The lesson that should be learned from MH370 is that you need to move quickly," said Charitha Pattiaratchi, an oceanographer at the University of Western Australia, referring to the Malaysia Airlines flight that went missing on March 8 during a trip from Kuala Lumpur to Beijing with 239 passengers and crew and which has not been found.